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Ready to stock up on rainbow trout

An angler tries his luck on the upper Colorado River. The fishing in the river upstream of Dotsero should improve with a plan from Colorado Parks and Wildlife to stock several thousand rainbow trout to replace fish killed by silt and debris earlier this year.

Colorado Parks and Wildlife is stocking whirling disease-resistant Hofer-cross rainbow trout in the Colorado River from Dotsero upstream six miles to the Cottonwood boat ramp. A storm last July killed most of the fish in this stretch and teh latest stocking program is expected to jump-start the fishery.

After a July rainstorm washed tons of debris and silt into the upper Colorado River upstream of Dotsero and subsequently killed nearly every fish in that stretch of the river, Colorado Parks and Wildlife saw the event as an opportunity to improve the fishery.

Tuesday morning, Parks and Wildlife biologists and other employees began stocking what they said were “several thousand” whirling disease-resistant rainbow trout in the river between Dotsero and the Cottonwood boat ramp six miles upstream.

“We have received recent reports from anglers that fishing has been unproductive and trout seem to have declined since the fish kill,” Parks and Wildlife aquatic biologist Kendall Bakich said. “Stocking these Hofer rainbows will not only replenish the population, it will establish a whirling disease-resistant fish that anglers can enjoy into the future.”

Whirling disease is caused by a water-borne parasite that attacks the soft cranial bones of young salmonids, including rainbow trout. Most of the young fish die before reaching six months of age.

Hofer rainbows are a hybrid cross between Gunnison River rainbow trout and whirling-disease-resistant rainbows discovered several years ago in a hatchery in Germany, where whirling disease is common.

The German rainbows initially came from U.S. trout eggs collected in the late 1800s near Gunnison and elsewhere, and generations of their progeny spent nearly a century in the German hatchery developing a resistance to whirling disease.

Once discovered by U.S. researchers seeking a solution to the whirling disease problem in U.S. waters, the Hofer trout have been crossbred with Gunnison River rainbows to develop a strain of fish with a resistance to whirling disease along with the tenacity, strength and survival instincts of Gunnison River fish.

According to Colorado Parks and Wildlife, it’s possible outbreaks of whirling disease may be linked to other, as-yet unidentified environmental factors.

Since its introduction in Colorado from a private hatchery in the late 1980s, the parasite has been confirmed in 13 of Colorado’s 15 major river drainages, including the Colorado, South Platte, Gunnison, Arkansas and Rio Grande rivers.

While the Colorado River continues to be infected with the whirling disease parasite, stocking the disease-resistant trout will improve the fishery for years to come, Parks and Wildlife managers said.

“The fish kill in July was unfortunate, but it has provided an opportunity to stock this disease resistant strain of rainbow trout,” said Perry Will, Parks and Wildlife area wildlife manager in Glenwood Springs. “Anglers fishing in this section of the Colorado River will certainly benefit from this effort.”